Method for working outer race of one-way clutch of roller type

ABSTRACT

The present invention provides a method for working an outer race of a one-way clutch of roller type comprising an outer race having pockets provided at their inner surfaces with cam surfaces, an inner race spaced inwardly from the outer race in a radial direction and disposed in concentric with the outer race, and a plurality of rollers disposed in the pockets and adapted to transmit torque between the outer race and the inner race when engaged by the cam surfaces, wherein the cam surfaces of the outer race are formed by milling working.

This application claims the benefit of Japanese Patent Application No. 2008-175776, filed Jul. 4, 2008, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for working or forming an outer race of a one-way clutch of roller type used as a part of a torque transmitting element or a back stop in a driving apparatus of a motor vehicle, an industrial machine and the like, for example.

2. Related Background Art

In general, a one-way clutch of roller type is comprised of an outer race, an inner race disposed in concentric with the outer race, a plurality of rollers disposed between an outer peripheral surface of the inner race and inner peripheral cam surfaces of the outer race and adapted to transmit torque, and springs contacted with idle rotation sides of the rollers.

With this arrangement, in the one-way clutch, the inner race is designed so as to be rotated only in one direction with respect to the outer race by means of a cam mechanism constituted by the rollers and the cam surfaces. That is to say, the inner race is designed so that it is idly rotated relative to the outer race in one direction, and on the other hand, it applies rotational torque to the outer race through the cam mechanism only in an opposite direction.

In the one-way clutch of roller type, there are provided pockets formed as deep recesses directed from an inner diameter side to an outer diameter side of the outer race, and cam surfaces having inner peripheries with which corresponding rollers are engaged are formed in the pockets.

In particular, in a one-way clutch of roller type of a motor bike, since the number of rollers is small (for example, three to six), if the respective rollers are not engaged securely, a design torque capacity may not be maintained.

For example, Japanese Patent Application Laid-open No. 2003-172377 discloses a technique in which cam surfaces which was conventionally formed by broach working is formed by cold press working.

However, in the broach working for forming the cam surfaces of the roller-type one-way clutch of this type, since the cam surface has a deep recess, a broaching tool must be lengthened, thereby increasing a tool cost and a manufacturing cost. Further, also regarding the abrasive re-polishing of a cutting edge of the broaching tool, a high cost is required.

Under these circumstances, regarding the few manufacturing number of parts, a ratio of the broach working cost is increased, thereby preventing reduction in cost.

In the conventional broach working, if recessed portions are previously formed in cam portions of a work piece or stock, a phase between the recessed portions and cam surface working cutting edges of the broaching tool will be deviated, with the result that the cutting edges are worn unevenly, thereby affecting a bad influence upon a service life of the broaching tool, and, thus, this technique could not be applied.

Further, cutting fluid for the broaching tool is oil and water-miscible cutting fluid was not used since it reduces the service life of the broaching tool. Thus, there arose an environmental problem.

Further, in the broach working, axial cutting scars are formed on the cam surfaces and this is not preferable for enhancing the anti-crack life of the outer race which is decreased by repeated loads applied to the one-way clutch.

Further, the working method described in the above-mentioned Japanese Patent Application Laid-open No. 2003-172377 has a disadvantage that the method is not suitable for an outer race having a great thickness.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a method for working or forming an outer race of a one-way clutch of roller type, in which cam surfaces of pockets are worked by milling working so that the method can cope with the few manufacturing number of parts flexibly, can reduce a cost of the part and can easily cope with different cam configurations.

To achieve the above object, the present invention provides a method for working an outer race of a one-way clutch of roller type comprising an outer race having pockets provided at their inner peripheries with cam surfaces, an inner race spaced inwardly from the outer race in a radial direction and disposed in concentric with the outer race, and a plurality of rollers disposed in the pockets and adapted to transmit torque between the outer race and the inner race when engaged by the cam surfaces, the method being characterized in that the cam surfaces of the outer race is formed by milling working.

Further, preferably, the outer race is formed as a ring shape having a hollow portion previously obtained by forging.

Further, preferably, the outer race is formed as a ring shape having a hollow portion previously obtained by forging and recessed portions are previously formed in an inner surface of the outer race at positions corresponding to the pockets.

According to the method for working the outer race of the one-way clutch of roller type of the present invention, the following effects can be obtained.

By working the cam surfaces of the outer race by the milling working, reduction in cost can be realized.

By working the cam surfaces by the milling working, the method can cope with the few manufacturing number of parts flexibly, thereby reducing the cost of the part. Further, by controlling the milling cutting by means of a computer, different cam configurations can easily be obtained.

In particular, the effect becomes excellent when many kinds of the few number of parts are manufactured. Further, by previously forming recessed portions in a stock or work piece of the outer race by means of forging, a cutting amount for the milling can be reduced, thereby reducing a working time and a material cost.

Further, although water-miscible cutting fluid was not used in the broach working since it reduces the service life of the broaching tool, in the milling working, water-miscible cutting fluid can be used, thereby improving an environmental problem.

Further, in the broach working, axial cutting scars are formed on the cam surfaces, with the result that the anti-crack life of the outer race which is decreased by repeated loads applied to the one-way clutch may be reduced. On the other hand, in the milling working, cutting scars are formed along a circumferential direction, which is more preferable for enhancement of the anti-crack life of the outer race.

In the conventional broach working, the recessed portions were not previously formed in the stock of the outer race. However, in the milling working, since the recessed portions can be formed previously, efficiency of the working is enhanced.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a one-way clutch of roller type according to an embodiment of the present invention.

FIG. 2 is a front view, partially in section, of the one-way clutch of FIG. 1, looked at from an opposite side in an axial direction.

FIG. 3 is an axial sectional view taken along the line 3-O-3 in FIG. 2.

FIG. 4 is view showing a completed outer race formed by milling working.

FIG. 5 is a front view of an outer race in which recessed portions are previously formed in an inner peripheral portion of the outer race.

FIG. 6 is a view showing a condition that the milling working is being performed by using an end mill.

DETAILED DESCRIPTION OF THE INVENTION

Now, embodiments of the present invention will be fully explained with reference to the accompanying drawings. Incidentally, it should be noted that the embodiments which will be described below are merely examples and other alterations and modifications can be made.

FIG. 1 is a front view showing a one-way clutch of roller type according to an embodiment of the present invention. FIG. 1 shows a condition that rollers are engaged by cam surfaces, i.e. a condition that the one-way clutch is locked. From this condition, when an outer race is rotated in a clockwise direction in FIG. 1, the locking condition is released, so that the one-way clutch is rotated idly.

As shown in FIG. 1, a one-way clutch 30 of roller type comprises an annular outer race 1 provided at its inner periphery with pockets 4 formed as recesses having cam surfaces 12, an inner race 2 (not shown in FIGS. 1 and 2, refer to FIG. 3) spaced inwardly from the outer race 1 in a radial direction and rotatably disposed in a concentric with the outer race and having an annular outer peripheral track surface 11, and a plurality of rollers 3 disposed in the pockets 4 and adapted to transmit torque between the outer peripheral track surface 11 of the inner race 2 and the cam surfaces 12.

Three pockets 4 equidistantly disposed in a circumferential direction are provided in the outer race 1 at its inner diameter side. Further, axially extending stepped rivet through holes 8 used for securing the outer race 1 to an associated member (not shown) are also provided to be equidistantly arranged in the circumferential direction. As shown in FIG. 1, the pockets 4 and the rivet holes 8 are arranged alternately and equidistantly in the circumferential direction. Further, it should be noted that the number of the pockets 4 can be selected in accordance with the magnitude of the torque, for example, between three and six.

FIG. 2 is a front view, partially in section, of the one-way clutch 30 of roller type of FIG. 1, looked at from an opposite side in an axial direction. Further, FIG. 3 is an axial sectional view taken along the line 3-O-3 in FIG. 2. As shown in FIG. 2, the one-way clutch 30 of roller type includes a holder 6 for holding the rollers 3, and the holder 6 comprises a cylindrical portion 10 and an annular flange portion 17 extending radially outwardly from an axial one end of the cylindrical portion 10. Further, the holder 6 has radially extending through windows 18 the number of which corresponds to the number of the rollers 3.

Each window 18 provided in the cylindrical portion 10 of the holder 6 extends through the cylindrical portion in the radial direction. However, in the axial direction, the window is closed at a side of the flange portion 17 and at a side of an end portion opposite to the flange portion 17. That is to say, the roller 3 is seated in the substantially rectangular window 18 and is supported by four sides of the window 18.

As shown in FIGS. 2 and 3, an annular stepped portion 13 is provided on an axial edge portion of the inner peripheral surface of the outer race 1, and the flange portion 17 of the holder 6 is engaged by the stepped portion 13. An axial depth of the stepped portion 13 is slightly greater than a thickness of the flange portion 17 so that, when the flange portion 17 is engaged by the stepped portion 13, a small clearance is created between an axial end surface 22 of the outer race 1 (end surface opposite to an axial end surface 21 in FIG. 1) and the axial end surface of the flange portion 17, thereby preventing interference with respect to the associated member. Further, an outer diameter of the stepped portion 13 is slightly greater than an outer diameter of the flange portion 17, so that the flange portion 17 is fitted in the stepped portion 13 with a predetermined clearance. In this way, the holder 6 is rotatable relative to the outer race 1.

Further, as shown in FIG.1 to FIG. 3, the one-way clutch 30 of roller type includes accordion springs 5 disposed in the corresponding pockets 4 and adapted to bias the rollers 3 toward an engagement direction with respect to the cam surfaces 12.

One end i.e. tab 15 of each accordion spring 5 is locked to an axial end surface 21 of the outer race 1, as shown in FIG. 1. Further, the other end 16 of the accordion spring 5 serves to hold an axial end face of the roller 3, as shown in FIG. 3.

The accordion spring 5 has a bellows portion 24 having a bellows-shaped configuration bent in the axial direction of the accordion spring 5 as shown in FIGS. 1 and 2. The bellows portion 24 can be expanded and contracted and serves to apply a biasing force to the roller 3 so that the roller 3 is engaged by the cam surface 12.

The tab 15 of the accordion spring 5 is secured to the axial end surface 21 of the outer race 1, for example, by welding, spot welding, adhesive, soldering or the like.

First Embodiment

Next, a method for forming or working the cam surface 12 of the outer race 1 according to the present invention will be explained. A ring-shaped stock or work piece for the outer race as a hollow member previously made of steel by forging is prepared. When assembled as the one-way clutch, the inner race 2 is fitted in the hollow portion.

At positions corresponding to positions where the pockets 4 are to be formed, each pocket 4 is being cut by milling working in an inner peripheral surface of the annular outer race stock from an opening side of the pocket 4. An end mill can be used to perform the milling working.

Although oil can be used as cutting fluid for the milling working, water-miscible cutting fluid can be used, and, when the water-miscible cutting fluid is used, an environmental problem is improved effectively.

FIG. 4 is a view showing a completed outer race 1 having three pockets 4 formed by the milling working along the circumferential direction. The entire pocket 4 is cut by the milling working. The end mill (refer to FIG. 6) is inserted into a hollow portion 43 of the outer race 1 from an axial direction, and each pocket 4 is being cut gradually from an opening portion 44 thereof. The cam surface 12 and a recessed portion 41 (into which the end of the accordion spring 5 is seated) to be provided in the pocket 4 are also formed by the milling working of the end mill.

Second Embodiment

FIG. 5 is a front view of an outer race in which recessed portions were previously formed in an inner peripheral surface of the outer race. The outer race 1 is formed as a ring shape having a hollow portion 43 previously formed by forging, and recessed portions 42 are previously formed in an inner diameter surface of the outer race at positions corresponding to the pockets 4.

Similar to the first embodiment, in correspondence to the positions where the pockets 4 are to be provided, each pocket 4 is being cut by the milling working in the inner peripheral surface of the annular outer race stock from the opening side of the pocket 4 to the recessed portion 42. In the second embodiment, areas 45 shown by the hatching lines in FIG. 5 are cut.

As is in the second embodiment, by previously providing the recessed portions in the outer race stock by the forging, a cutting amount for the milling working can be reduced. Thus, a working time can be shortened and a material cost can be reduced.

In the conventional broach working, although it was difficult to form recessed portions for the cam portions in the stock, in the milling working, the recessed portions can be formed previously.

FIG. 6 is a view showing a condition that the milling working is being performed by means of the end mill. The end mill 46 is provided at its side surface 47 with cutting edges. By feeding the end mill against the inner peripheral surface of the pocket 4, the pocket 4 is cut. As can be seen from the completed outer race 1 shown in FIG. 4, the end mill 46 serves to cut the pocket along a curved configuration of the pocket. As shown in FIG. 6, since the cutting scars is created in the cam surface 12 by the milling working along the circumferential direction, in comparison with the broach working in which the cutting scars are created in the axial direction, the milling working is more preferable for the enhancement of the anti-crack life of the outer race.

By forming the cam surface 12 by the milling working, the method can cope with the few manufacturing number of parts flexibly, thereby reducing the cost of the part. Further, by controlling the milling cutting by means of a computer (not shown), different cam configurations can easily be obtained.

The present invention can be applied to a part of a torque transmitting elements or back stop in a driving apparatus of a motor vehicle, an industrial machine and the like, and, particularly, when the present invention is applied to a motor bike, an excellent effect can be achieved.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 

1. A method for working an outer race of a one-way clutch of roller type comprising an outer race having pockets provided at their inner surfaces with cam surfaces, an inner race spaced inwardly from said outer race in a radial direction and disposed in concentric with said outer race, and a plurality of rollers disposed in said pockets and adapted to transmit torque between said outer race and said inner race when engaged by said cam surfaces, wherein: said cam surfaces of said outer race are formed by milling working.
 2. An outer race working method according to claim 1, wherein said outer race is formed as a ring shape having a hollow portion previously obtained by forging.
 3. An outer race working method according to claim 1, wherein said outer race is formed as a ring shape having a hollow portion previously obtained by forging and recessed portions are previously formed in an inner surface of said outer race at positions corresponding to said pockets. 